Watermarks that change pixel values can cause secondary changes to adjacent parts of the imagery that use the changed pixels as a reference. Watermarks that change motion vector values can cause secondary changes to adjacent parts of the imagery that use the changed motion vectors as a reference.
Propagation maps have been used in a fidelity criterion (PCT/US09/004702 and PCT/US09/004752) to ensure that a proposed change will not introduce fidelity artifacts anywhere in the propagation path.
In H.264/AVC, a two-step watermarking modifies one block at a time. The watermark detector then analyzes that one block in the process of recovering the watermark payload. This method suffers when the watermarked content undergoes a geometric distortion prior to watermark recovery. Slight misalignments result in a large percentage of the target block being missed by the detector and can yield unreliable detection.
As such, a need exists for an improved watermark detection method that can capture geometric distortions that current detection schemes miss.